const DECRYPT = 0;
const ROUND = 32;
const BLOCK = 16;

const Sbox = [
    0xd6, 0x90, 0xe9, 0xfe, 0xcc, 0xe1, 0x3d, 0xb7, 0x16, 0xb6, 0x14, 0xc2, 0x28, 0xfb, 0x2c, 0x05,
    0x2b, 0x67, 0x9a, 0x76, 0x2a, 0xbe, 0x04, 0xc3, 0xaa, 0x44, 0x13, 0x26, 0x49, 0x86, 0x06, 0x99,
    0x9c, 0x42, 0x50, 0xf4, 0x91, 0xef, 0x98, 0x7a, 0x33, 0x54, 0x0b, 0x43, 0xed, 0xcf, 0xac, 0x62,
    0xe4, 0xb3, 0x1c, 0xa9, 0xc9, 0x08, 0xe8, 0x95, 0x80, 0xdf, 0x94, 0xfa, 0x75, 0x8f, 0x3f, 0xa6,
    0x47, 0x07, 0xa7, 0xfc, 0xf3, 0x73, 0x17, 0xba, 0x83, 0x59, 0x3c, 0x19, 0xe6, 0x85, 0x4f, 0xa8,
    0x68, 0x6b, 0x81, 0xb2, 0x71, 0x64, 0xda, 0x8b, 0xf8, 0xeb, 0x0f, 0x4b, 0x70, 0x56, 0x9d, 0x35,
    0x1e, 0x24, 0x0e, 0x5e, 0x63, 0x58, 0xd1, 0xa2, 0x25, 0x22, 0x7c, 0x3b, 0x01, 0x21, 0x78, 0x87,
    0xd4, 0x00, 0x46, 0x57, 0x9f, 0xd3, 0x27, 0x52, 0x4c, 0x36, 0x02, 0xe7, 0xa0, 0xc4, 0xc8, 0x9e,
    0xea, 0xbf, 0x8a, 0xd2, 0x40, 0xc7, 0x38, 0xb5, 0xa3, 0xf7, 0xf2, 0xce, 0xf9, 0x61, 0x15, 0xa1,
    0xe0, 0xae, 0x5d, 0xa4, 0x9b, 0x34, 0x1a, 0x55, 0xad, 0x93, 0x32, 0x30, 0xf5, 0x8c, 0xb1, 0xe3,
    0x1d, 0xf6, 0xe2, 0x2e, 0x82, 0x66, 0xca, 0x60, 0xc0, 0x29, 0x23, 0xab, 0x0d, 0x53, 0x4e, 0x6f,
    0xd5, 0xdb, 0x37, 0x45, 0xde, 0xfd, 0x8e, 0x2f, 0x03, 0xff, 0x6a, 0x72, 0x6d, 0x6c, 0x5b, 0x51,
    0x8d, 0x1b, 0xaf, 0x92, 0xbb, 0xdd, 0xbc, 0x7f, 0x11, 0xd9, 0x5c, 0x41, 0x1f, 0x10, 0x5a, 0xd8,
    0x0a, 0xc1, 0x31, 0x88, 0xa5, 0xcd, 0x7b, 0xbd, 0x2d, 0x74, 0xd0, 0x12, 0xb8, 0xe5, 0xb4, 0xb0,
    0x89, 0x69, 0x97, 0x4a, 0x0c, 0x96, 0x77, 0x7e, 0x65, 0xb9, 0xf1, 0x09, 0xc5, 0x6e, 0xc6, 0x84,
    0x18, 0xf0, 0x7d, 0xec, 0x3a, 0xdc, 0x4d, 0x20, 0x79, 0xee, 0x5f, 0x3e, 0xd7, 0xcb, 0x39, 0x48
];

const CK = [
    0x00070e15, 0x1c232a31, 0x383f464d, 0x545b6269,
    0x70777e85, 0x8c939aa1, 0xa8afb6bd, 0xc4cbd2d9,
    0xe0e7eef5, 0xfc030a11, 0x181f262d, 0x343b4249,
    0x50575e65, 0x6c737a81, 0x888f969d, 0xa4abb2b9,
    0xc0c7ced5, 0xdce3eaf1, 0xf8ff060d, 0x141b2229,
    0x30373e45, 0x4c535a61, 0x686f767d, 0x848b9299,
    0xa0a7aeb5, 0xbcc3cad1, 0xd8dfe6ed, 0xf4fb0209,
    0x10171e25, 0x2c333a41, 0x484f565d, 0x646b7279
];

function rotl(x, y) {
    return x << y | x >>> (32 - y);
}

function byteSub(a) {
    return (Sbox[a >>> 24 & 0xFF] & 0xFF) << 24 | (Sbox[a >>> 16 & 0xFF] & 0xFF) << 16 | (Sbox[a >>> 8 & 0xFF] & 0xFF) << 8 | (Sbox[a & 0xFF] & 0xFF);
}

function l1(b) {
    return b ^ rotl(b, 2) ^ rotl(b, 10) ^ rotl(b, 18) ^ rotl(b, 24);
}

function l2(b) {
    return b ^ rotl(b, 13) ^ rotl(b, 23);
}

function sms4Crypt(input, output, roundKey) {
    let r;
    let mid;
    let x = new Array(4);
    let tmp = new Array(4);
    for(let i = 0; i < 4; i++) {
        tmp[0] = input[0 + 4 * i] & 0xff;
        tmp[1] = input[1 + 4 * i] & 0xff;
        tmp[2] = input[2 + 4 * i] & 0xff;
        tmp[3] = input[3 + 4 * i] & 0xff;
        x[i] = tmp[0] << 24 | tmp[1] << 16 | tmp[2] << 8 | tmp[3];
    }

    for(r = 0; r < 32; r += 4) {
        mid = x[1] ^ x[2] ^ x[3] ^ roundKey[r + 0];
        mid = byteSub(mid);
        x[0] = x[0] ^ l1(mid); // x4
        
        mid = x[2] ^ x[3] ^ x[0] ^ roundKey[r + 1];
        mid = byteSub(mid);
        x[1] = x[1] ^ l1(mid); // x5
        
        mid = x[3] ^ x[0] ^ x[1] ^ roundKey[r + 2];
        mid = byteSub(mid);
        x[2] = x[2] ^ l1(mid); // x6
        
        mid = x[0] ^ x[1] ^ x[2] ^ roundKey[r + 3];
        mid = byteSub(mid);
        x[3] = x[3] ^ l1(mid); // x7
    }
    
    //Reverse
    for(let j = 0; j < 16; j += 4) {
        output[j] = x[3 - j / 4] >>> 24 & 0xff;
        output[j+1] = x[3 - j / 4] >>> 16 & 0xff;
        output[j+2] = x[3 - j / 4] >>> 8 & 0xff;
        output[j+3] = x[3 - j / 4] & 0xff;
    }
}

function sms4KeyExt(key, roundKey, cryptFlag) {
    let r;
    let mid;
    let x = new Array(4);
    let tmp = new Array(4);

    for (let i = 0; i < 4; i++) {
        tmp[0] = key[0 + 4 * i] & 0xff;
        tmp[1] = key[1 + 4 * i] & 0xff;
        tmp[2] = key[2 + 4 * i] & 0xff;
        tmp[3] = key[3 + 4 * i] & 0xff;
        x[i] = tmp[0] << 24 | tmp[1] << 16 | tmp[2] << 8 | tmp[3];
    }

    x[0] ^= 0xa3b1bac6;
    x[1] ^= 0x56aa3350;
    x[2] ^= 0x677d9197;
    x[3] ^= 0xb27022dc;

    for(r = 0; r < 32; r += 4) {
        mid = x[1] ^ x[2] ^ x[3] ^ CK[r+0];
        mid = byteSub(mid);
        roundKey[r + 0] = x[0] ^= l2(mid); // roundKey0 = K4
        
        mid = x[2] ^ x[3] ^ x[0] ^ CK[r+1];
        mid = byteSub(mid);
        roundKey[r + 1] = x[1] ^= l2(mid); // roundKey1 = K5
        
        mid = x[3] ^ x[0] ^ x[1] ^ CK[r+2];
        mid = byteSub(mid);
        roundKey[r + 2] = x[2] ^= l2(mid); // roundKey2 = K6
        
        mid = x[0] ^ x[1] ^ x[2] ^ CK[r + 3];
        mid = byteSub(mid);
        roundKey[r + 3] = x[3] ^= l2(mid); // roundKey3 = K7
    }
        
    // 解密时轮密钥使用顺序：roundKey31, roundKey30, ..., roundKey0
    if(cryptFlag === DECRYPT) {
        for(r = 0; r < 16; r++) {
            mid = roundKey[r];
            roundKey[r] = roundKey[31 - r];
            roundKey[31 - r] = mid;
        }
    }
}

function sm4(inArray, key, cryptFlag) {
    let outArray = [];
    let point = 0;
    let roundKey = new Array(ROUND); 
    sms4KeyExt(key, roundKey, cryptFlag);

    let input = new Array(16);
    let output = new Array(16);

    let inLen = inArray.length;
    while (inLen >= BLOCK) {
        input = inArray.slice(point, point + 16);
        sms4Crypt(input, output, roundKey);
        
        for (let i = 0; i < BLOCK; i++) {
            outArray[point + i] = output[i];
        }

        inLen -= BLOCK;
        point += BLOCK;
    }

    return outArray;
}

module.exports = {
    encrypt(inArray, key) {
        return sm4(inArray, key, 1);
    },
    decrypt(inArray, key) {
        return sm4(inArray, key, 0);
    }
};
